The relation to ex runs as follows: ex in pentic subsymmetry can be given as xffoo3oxoof3fooxo3ooffx&#zx.
That will be transformed into xFfoo3o(-x)oof3fxoxo3ooffx&#zx.
Then a Stott expansion wrt. the second node produces this polychoron.

The non-existing lacings calculate to vertex distances according to f=(1+sqrt(5))/2.